package panda.io;

import java.io.Serializable;
import java.io.Writer;

/**
 * {@link Writer} implementation that outputs to a {@link StringBuilder}.
 * <p>
 * <strong>NOTE:</strong> This implementation, as an alternative to
 * <code>java.io.StringWriter</code>, provides an <i>un-synchronized</i> (i.e. for use in a single
 * thread) implementation for better performance. For safe usage with multiple {@link Thread}s then
 * <code>java.io.StringWriter</code> should be used.
 * 
 * @author yf.frank.wang@gmail.com
 */
public class StringBuilderWriter extends Writer implements Serializable {
	private static final long serialVersionUID = 1L;

	private final StringBuilder builder;

	/**
	 * Construct a new {@link StringBuilder} instance with default capacity.
	 */
	public StringBuilderWriter() {
		this.builder = new StringBuilder();
	}

	/**
	 * Construct a new {@link StringBuilder} instance with the specified capacity.
	 * 
	 * @param capacity The initial capacity of the underlying {@link StringBuilder}
	 */
	public StringBuilderWriter(int capacity) {
		this.builder = new StringBuilder(capacity);
	}

	/**
	 * Construct a new instance with the specified {@link StringBuilder}.
	 * 
	 * @param builder The String builder
	 */
	public StringBuilderWriter(StringBuilder builder) {
		this.builder = builder != null ? builder : new StringBuilder();
	}

	/**
	 * Append a single character to this Writer.
	 * 
	 * @param value The character to append
	 * @return This writer instance
	 */
	@Override
	public Writer append(char value) {
		builder.append(value);
		return this;
	}

	/**
	 * Append a character sequence to this Writer.
	 * 
	 * @param value The character to append
	 * @return This writer instance
	 */
	@Override
	public Writer append(CharSequence value) {
		builder.append(value);
		return this;
	}

	/**
	 * Append a portion of a character sequence to the {@link StringBuilder}.
	 * 
	 * @param value The character to append
	 * @param start The index of the first character
	 * @param end The index of the last character + 1
	 * @return This writer instance
	 */
	@Override
	public Writer append(CharSequence value, int start, int end) {
		builder.append(value, start, end);
		return this;
	}

	/**
	 * Closing this writer has no effect.
	 */
	@Override
	public void close() {
	}

	/**
	 * Flushing this writer has no effect.
	 */
	@Override
	public void flush() {
	}

	/**
	 * Write a String to the {@link StringBuilder}.
	 * 
	 * @param value The value to write
	 */
	@Override
	public void write(String value) {
		if (value != null) {
			builder.append(value);
		}
	}

	/**
	 * Write a portion of a character array to the {@link StringBuilder}.
	 * 
	 * @param value The value to write
	 * @param offset The index of the first character
	 * @param length The number of characters to write
	 */
	@Override
	public void write(char[] value, int offset, int length) {
		if (value != null) {
			builder.append(value, offset, length);
		}
	}

	/**
	 * Return the underlying builder.
	 * 
	 * @return The underlying builder
	 */
	public StringBuilder getBuilder() {
		return builder;
	}

	/**
	 * Returns {@link StringBuilder#toString()}.
	 * 
	 * @return The contents of the String builder.
	 */
	@Override
	public String toString() {
		return builder.toString();
	}
}
